12 



AN INTRODUCTION TO ENTOMOLOGY. 



6' 



Fig. 



-Mouth-parts of the Red- 

 legged Locust. 



The Mouth-parts. 

 The mouth-parts (Fig. 22) consist typically of an upper lip, labrum 

 (8), an under lip, labium (12), and two 

 pairs of jaws acting horizontally between 

 them. The upper pair of jaws are called 

 the mandibles (10); the lower pair, the 

 maxillce (n). The maxillae and labium 

 are each furnished with a pair of feelers, 

 called respectively the maxillary palpi 

 (lid), and the labial palpi (i2d). There 

 may be also within the mouth one or two 

 tongue-like organs, the cpipJiarynx (9) and 

 hypopharynx (13). 



No set of organs in the body of an insect 

 vary in form to a greater degree than do the 

 mouth-parts. Thus with some the mouth is 

 formed for biting, while with others it is formed 

 for sucking. Among the biting insects some are predaceous, and have jaws 

 fitted for seizing and tearing their prey ; others feed upon vegetable matter, 

 and have jaws for chewing this kind of food. Among the sucking insects 

 the butterfly merely sips the nectar from flowers, while the mosquito needs a 

 powerful instrument for piercing its victim. In this chapter the typical form 

 of the mouth-parts as illustrated by the biting insects is described. The 

 various modifications of it presented by the sucking insects are described later, 

 in the discussions of the characters of those insects.* 



The Labrum.— The. labrum or upper lip (8) is an appendage of the cephalic 

 margin of the dorsal part of the head. It is usually a narrow transverse sclerite. 

 In some insects it is large and projecting, and often notched ; in others it is 

 concealed beneath a largely developed clypeus. 



The Mandibles. — The mandibles (10) are the dorsal pair of jaws. They vary 

 much in form, but are usually three-sided, with their lateral t surface more or 



* The more important papers on the nomenclature of the parts of the mouth in biting 

 insects are the following: 



Kirby and Spenxe. Introduction to Entomology, vol. III. (1818.) 



MacLeav, W. S. Horae entomologicae (2 vols., 1819, 1821). This work I have not 



Straus-Durckheim, H. E. Considerations generate sur l'anatomie des animaux 

 articules. (1828.) 



Newman, Edward. A paper on the nomenclature of the parts of the head of insects. 



(1834.) 



Newport, G. The article " Insecta," Todd's Cycl. of Anat. and Physiol. (1839.) 

 Brulle, A. Recherches sur les transformations des appendices dans les Articules. 



Annales des Sciences Naturelles, t. II. (1844.) 



f I have not attempted to determine the normal position of the mouth-parts, but have 



described each with its distal end directed cephalad. This seems to me the way least 



likely to lead to confusion. 



